[TriLUG] How to spawn separate process and get pid.

[Brian Weaver]

You can do it in bash using something similar to the following:

#!/bin/bash
# $@ represents all the arguments except the name of the program '$0'
#
# this executes the command in the background and kills it after 10
# minutes if it is still running.
#
$@ >/dev/null 2>&1 &
pid=$!
sleep 600
if kill -0 $pid >/dev/null 2>&1 ; then
	# still alive, but not for long
	kill -HUP $pid
	sleep 2
	if kill -0 $pid >/dev/null 2>&1 ; then
		kill -TERM $pid
		sleep 2
		if kill -0 $pid >/dev/null 2>&1 ; then 
			kill -KILL $pid # murder it!
		fi
	fi
fi
# end of script.

I don't promise the above script is error free, but you get the idea.
'$!' represents the pid of the last background process. You might want
to 'disown' the process after you have the pid too.

-Weave

Wesley Zhang [xyzhang at cisco.com] wrote on Fri, Jan 21, 2005 at 11:49:15AM -0500:
> Hi All,
> 
> I am a newbie on shell script. But I would like to use linux shell 
> script to control a job that runs forever and will be terminated after 
> 10 minute. My thought for this is following:
> 
>  pid = start-job-for ("cmd") // has to be a separate process
>  sleep 10 min
>  kill pid.
> 
> How can I spawn a separate process to execute my command and get the 
> proper process id?
> 
> Thanks,
> Wesley
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